Anastomosis, or joining of severed blood vessels, is among the vital and time consuming tasks associated with surgical procedures. Hence, the success of a given surgical procedure may hinge upon the degree of circulation restored to the interconnected vessels through such anastomosis procedure.
A wide variety of anastomosis devices and methods have been developed for anastomosing ends of living vessels. One known procedure for anastomosing blood vessels includes the use of sutures, i.e., stitches. One known shortcoming with conventional suturing techniques is their tendency to be relatively tedious, particularly with blood vessels of small diameters, such as vessels being one millimeter or less in diameter. Experience has revealed that this is especially the case when anastomosing children's vessels because they are even smaller and prone to spasm. In addition, successful anastomosing of blood vessels is highly dependent on the proper placement of the sutures by the surgeon. Thus, in certain instances, such known conventional suturing anastomosing techniques are time-consuming to a point that undesirable extends the duration of a surgical procedure.
With the exception of the aorta and vena cava, human blood vessels have a naturally occurring contractility known as circumferential compressive stress which resists dilation. As the vessel diameter decreases and the relative wall thickness increases, these compressive forces become proportionately larger. Radial tethering forces of tissues do exist around the vessel, but these are of lesser significance than longitudinal vessel motion tethering. It is therefore important to consider these forces to assure patency, i.e., the vessels ability to conduct blood flow, at the anastomosis site.
Even successful suturing of blood vessels does not assure continued patency at the sutured site. It is known that clotting of blood, known as "thrombosis," may act to block blood flow through an anastomosed vessel. In addition to the already mentioned forces, thrombosis after microvascular repair may be caused by a number of other factors which include inaccurate placement of sutures, vessel spasms, stenosis and microclamp damage. Furthermore, it has been found that continuity of flow during the first twenty minutes after anastomosis is critical in preventing thrombus formation and that platelet aggregation, and later resolution, occurs in the first several hours after a microvascular anastomosis. Hence, it is critical that anastomosing procedures employ effective devices and be performed relatively quickly to relieve the procedure of the above-mentioned shortcomings.
To aid in anastomosing blood vessels, a number of implantable devices have been employed at the anastomosis site for assisting to interconnect severed ends of blood vessels. Such devices, and methods for employing the same, are disclosed in U.S. Pat. Nos. 3,254,650 and 4,055,186, British Patent No. 1,181,563, German Fed. Rep. Patent No. 2,101,282 and Nakayama et al. Surgery December 1962, pp. 918-931. Other devices, such as that disclosed in U.S. Pat. No. 2,180,337, have the severed ends of the blood vessels everted over the device to facilitate suturing.
Another known device for aiding in anastomosing blood vessels is disclosed in U.S. Pat. No. 4,474,181. This patent discloses an implantable external ring to which a pair of vessels, having prepared openings, may be tethered with sutures so as to hold their intima in fluid-tight apposition. The ring maintains the lumen of the vessels in an expanded condition at the anastomosis site, which tends to provide assurance of patency. Hence, this device is highly effective for providing patency at the anastomosis site by countering the already mentioned concerns pertaining to thrombosis at the susceptible site, i.e., the anastomosis site.
However, one known shortcoming with suturing the vessel ends at the ring is the difficulty of this procedure, particularly for relatively small vessels, and the time demands. In a typical surgical procedure, a large number of vessels my require anastomosis, in which many of these are relatively small vessels, and the time consumed anastomosing vessels by suturing contributes significantly to the overall time necessary to complete the surgical procedure. It would therefore be desirable and advantageous to reduce the anastomosis time by avoiding the use of sutures altogether.
One known solution attempting to solve the disadvantages associated with suturing at a ring is disclosed in A. D. Donetskii, Eksperim Khirur pp. 153-59 (1956). The disclosed device includes an anastomosis ring having radially and outwardly extending protrusions for impaling the vessel ends, and thereby securing them in apposition at the ring. More particularly, the end of the first vessel is initially inserted through the ring opening and then everted around and over the outside surface of the ring and impaled on the radial protrusions, and then, the end of the second vessel is drawn over the everted first vessel end and also impaled on the radial protrusions.
one known shortcoming with simply impaling the vessel ends at the ring with the known radial protrusions is that some of the smaller and weaker vessels tend to tear during the anastomosis procedure. That is, with a ring having three radially and outwardly extending protrusions, the vessel ends tend to tear while the vessel is being stretched to be impaled on the third protrusion after first being impaled on two of the protrusions. More specifically, since appropriately proportioned rings have inside surfaces slightly smaller than the unstressed or relaxed exterior diameter of the vessel ends and exterior diameters slightly larger than the relaxed exterior diameter of the vessel, there is seldom a problem in impaling the vessel on the first two of the protrusions, but tearing often occurs when stretching the vessel to impale it on the third. Thus, it is desirable to avoid vessel tearing during the impaling process to provide a stable, patent anastomosis.
One known solution to tearing of vessels is disclosed in U.S. Pat. No. 4,693,249, issued to Schenck et al., as an anastomosis ring which is shiftable between a contracted state and an expanded state. More specifically, as disclosed, the ring is contracted when the vessels are being interconnected and impaled on all of the protrusions and, then, is expanded to open more fully the vessel lumens for liquid flow therethrough.
It is a primary object of the present invention to provide a new and improved sutureless, extraluminary anastomosis device and method for interconnecting a first and second living vessel which reduces potential for tearing the vessels during the anastomosis procedure and assures patency at the anastomosis site.
It is another object of the present invention to provide such device and method in a manner which reduces the time consumption necessary for anastomosing ends of living vessels, which results in overall shortening of the surgical procedure.
An overall object of the present invention is to provide an anastomosis device which is efficient and cost effective to manufacture.